update on fall air quality in beijing

Yesterday a friend commented that it seems like the air quality in Beijing this fall has been much better than last fall. Turns out he's right:

(For background, see this post on Air Pollution Index (API)).

Although the air quality since 9/21 hasn't been as good as it was during the Olympic period, the average particulate matter concentration in the air this fall has been over 20% lower than the same time period last year and almost 40% lower than the same time period two years ago. Perhaps the one-day-a-week car ban is working?

FYI, the average PM10 concentration this fall of around 100 ug/m^3 is actually right at China's annual air quality target, though still five times higher than the WHO recommended annual level of 20 ug/m^3.

Lastly, I want to show again a long time-scale graph of daily API vs. time in Beijing:

There are two main take-away messages from this graph:

1) The improved air quality of the Olympic period (7/20 - 9/20, 2008) is quite apparent.
2) We have yet to see a major pollution spike (say, API above 200) since the Olympics ended...